Research Of The Thermal Performance Of Light Composite Building Envelope

At present,the use of light composite building envelope in China has developed rapidly.But thermal performance of these structures are lack of clear definition, requirements and calculation methods in the current thermal design code for civil building and the design standard for energy efficiency.The typical light composite roofs are classified into two types in the paper:roof board & membrane construction.There are different constructions and material introductions of these two types.This paper has bringed up that the thermal conductivity can not used in the evaluation of thermal performance of membrane construction.Radiation heat transfer is crucial to the thermal performance,so we must consider long wave radiation.The membrane construction will cause vertical temperture stratification and condensation becaues of its thermal mass and hydrophobicity.Through experiments of the thermal performance of light composite roof in winter and summer,the paper has made an analysis of thermal stability based on periodic heat transfer process.Analysis of the thermal environment has showed that the people in light composite building beared higher HSI in summer and stronger cooling radiation. The paper also bringed up that condensation must be within the construction.The paper proposed that the periodic heat transfer process and permit amplitude only evaluated the envelope by D can not meet the requirements now.The other methods also has a number of shortcomings.The paper has established a new Degree-Days Value for the light composite building envelope.